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Este estudo investigou a eficácia biomecânica de infraestruturas de próteses feitas de cobalto-cromo (CoCr) e compósito de fibra de vidro (FVRC), implantadas em mandíbulas edêntulas. A distribuição de densidade foi investigada utilizando um modelo ósseo sintético, equipado com extensômetros, para simular condições anatômicas e biomecânicas humanas. Os implantes de conexão interna cone morse fabricados pela Conexão Sistemas de Próteses, Arujá, São Paulo, Brasil, têm diâmetro e comprimento de 4.0mm e 13mm, respectivamente, e os intermediários protéticos selecionados foram Micro Unit Sólidos da mesma marca para plataforma cone morse, com altura de transmucoso 2,5 mm, foram utilizados para suportar as infraestruturas de próteses híbridas. Por meio de extensometria, mediu-se a deformação óssea sob carga ao redor dos quatro implantes, comparando as performances das infraestruturas CoCr e FVRC. Os resultados revelaram informações importantes sobre a seleção de materiais para infraestruturas de próteses, com foco específico nas barras de FVRC e CoCr. Os testes "in vitro" e análises estatísticas destacaram que as barras de FVRC produziram menores microdeformações em comparação com as de CoCr sob carga. Essa diferença foi estatisticamente significativa, indicando que a FVRC possui uma capacidade superior de absorver e distribuir carga de maneira mais eficiente. No entanto, ressalta-se a necessidade de estudos futuros, incluindo pesquisas clínicas, para explorar totalmente as implicações desses achados e aprimorar ainda mais as práticas de reabilitação oral com implantes (AU)

This study investigated the biomechanical effectiveness of prosthetic infrastructures made of cobalt-chromium (CoCr) and fiberglass composite (FGC), implanted in edentulous jaws. The density distribution was investigated using a synthetic bone model, equipped with strain gauges, to simulate human anatomical and biomechanical conditions. The morse cone internal connection implants manufactured by Conexão Sistemas de Próteses, Arujá, São Paulo, Brazil, have a length of 4.0mm and 13mm, respectively, and the prosthetic intermediates selected were Micro Unit Solids of the same brand for a morse cone platform, with a transmucosal height of 2.5 mm, were used to support hybrid prosthetic infrastructures. Using extensometry, bone deformation under load around the four implants was measured, comparing with the performance of the CoCr and FGC infrastructures. The results revealed important information about the selection of materials for prosthetic infrastructures, with a specific focus on FGC and CoCr bars. "In vitro" tests and statistical analyzes highlighted that FGC bars produced smaller microdeformations compared to CoCr bars under load. This difference was statistically significant, demonstrating that FGC has a superior capacity to absorb and distribute load more efficiently. However, the need for future studies, including clinical research, is highlighted to fully explore the implications of these findings and further improve oral rehabilitation practices with implants. (AU)

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The aluminum has mechanical properties enable to a better finishing in welded region. However, it fails eventually when a dynamic load is applied. This study estimated the damage by multiaxial fatigue present in welded joints of bicycle frames, the methodologies of analysis are based on Findley's and Dang Van's Methods. Seven experiments were performed on two pipes with welded joints. These pipes were choosen according to Bike S/A data, numerical simulations in bicycle frame and previous analysis of specialized literature. Therefore, lifespan result of frame, in function the distance, is 3 × 1 0 4 km - 5.5 × 1 0 4 km.

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This study aimed to evaluate the biomechanical behavior of Morse taper implants using different abutments (CMN abutment [(CMN Group] and miniconical abutments [MC Group]), indicated to support a screw-retained 3-unit fixed partial denture. For the in vitro test, polyurethane blocks were fabricated for both groups (n = 10) and received three implants in the "offset" configuration and their respective abutments (CMN or MC) with a 3-unit fixed partial denture. Four strain gauges were bonded to the surface of each block. For the finite element analysis, 3D models of both groups were created and exported to the analysis software to perform static structural analysis. All structures were considered homogeneous, isotropic, and elastic. The contacts were considered non-linear with a friction coefficient of 0.3 between metallic structures and considered bonded between the implant and substrate. An axial load of 300 N was applied in three points (A, B, and C) for both methods. The microstrain and the maximum principal stress were considered as analysis criteria. The obtained data were submitted to the Mann-Whitney, Kruskal-Wallis, and Dunn's multiple comparison test (α = 5%). The results obtained by strain gauge showed no statistical difference (p = 0.879) between the CMN (645.3 ± 309.2 µÎµ) and MC (639.3 ± 278.8 µÎµ) and allowed the validation of computational models with a difference of 6.3% and 6.4% for the microstrains in the CMN and MC groups, respectively. Similarly, the results presented by the computational models showed no statistical difference (p = 0.932) for the CMN (605.1 ± 358.6 µÎµ) and MC (598.7 ± 357.9 µÎµ) groups. The study concluded that under favorable conditions the use of CMN or MP abutments to support a fixed partial denture can be indicated.

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In many areas, the analysis of a cylindrical structure is necessary, and a form to analyze it is by evaluating the diameter changes. Some areas can be cited: pipelines for oil or gas distribution and radial growth of trees whose diameter changes are directly related to irrigation and the radial expansion since it depends on the water soil deficit. For some species, these radial variations can change in around 5 mm. This paper proposes and experimentally investigates a sensor based on a core diameter mismatch technique for diameter changes measurement. The sensor structure is a combination of a cylindrical piece developed using a 3D printer and a Mach-Zehnder interferometer. The pieces were developed to assist in monitoring the diameter variation. It is formed by splicing an uncoated short section of MMF (Multimode Fiber) between two standard SMFs (Singlemode Fibers) called SMF-MMF-SMF (SMS), where the MMF length is 15 mm. The work is divided into two main parts. Firstly, the sensor was fixed at two points on the first developed piece, and the diameter reduction caused dips or peaks shift of the transmittance spectrum due to curvature and strain influence. The fixation point (FP) distances used are: 5 mm, 10 mm, and 15 mm. Finally, the setup with the best sensitivity was chosen, from first results, to develop another test with an optimization. This optimization is performed in the printed piece where two supports are created so that only the strain influences the sensor. The results showed good sensitivity, reasonable dynamic range, and easy setup reproduction. Therefore, the sensor could be used for diameter variation measurement for proposed applications.

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INTRODUCTION: The present study aimed to describe an in vitro study model to investigate root surface strain (RSS) and its correlation with the initiation/propagation of microcracks during different endodontic procedures. METHODS: Four lower human incisors extracted microcrack free were selected by micro-computed tomographic imaging. Two strain gauges were bonded to the root surface of each incisor. Then, the teeth were prepared to reproduce the periodontal ligament artificially. The gauges were attached to a data acquisition system. The RSS was recorded during the entire endodontic procedure, which consisted of accessing the endodontic cavity, cleaning, shaping preparation with an Mtwo rotary system (VDW, Munich, Germany), and filling with a standardized technique. Each incisor was submitted to a different retreatment protocol and supplementary cleaning method as follows: (1) Reciproc (RC, VDW) + Flatsonic (FS; Helse, Santa Rosa de Viterbo, Brazil), (2) RC + XP-endo Finisher (XPF; FKG Dentaire, La Chaux-de-Fonds, Switzerland), (3) Mtwo retreatment (MR) + FS, and (4) MR + XPF. Finally, the teeth were rescanned to establish the postoperative microcrack formation by 2 well-trained and blinded examiners. RESULTS: The maximum and minimum RSS values were -120 and 510 microstrains, respectively, for all of the files. RC showed the highest RSS values during endodontic retreatment compared with MR. FS demonstrated a higher variation between the minimum and maximum RSS than XPF. No microcracks were observed in the specimens. CONCLUSIONS: This preliminary study proposed an experimental model that would combine 2 methods to evaluate the effects of endodontic systems on dentin. Although strain gauges would provide data on the stresses created, the pre- and postoperative evaluation of micro-computed tomographic images would enable microcrack formation to be determined.

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This paper presents the development and validation of a polymer optical-fiber strain-gauge sensor based on the light-coupling principle to measure axial deformation of elastic tendons incorporated in soft actuators for wearable assistive robots. An analytical model was proposed and further validated with experiment tests, showing correlation with a coefficient of R = 0.998 between experiment and theoretical data, and reaching a maximum axial displacement range of 15 mm and no significant hysteresis. Furthermore, experiment tests were carried out attaching the validated sensor to the elastic tendon. Results of three experiment tests show the sensor's capability to measure the tendon's response under tensile axial stress, finding 20.45% of hysteresis in the material's response between the stretching and recovery phase. Based on these results, there is evidence of the potential that the fiber-optical strain sensor presents for future applications in the characterization of such tendons and identification of dynamic models that allow the understanding of the material's response to the development of more efficient interaction-control strategies.

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Objetivo: avaliar, por meio de extensometria, a infl uência da flange do implante de titânio na deformação superficial do osso. Material e métodos: um bloco de poliuretano simulando um osso tipo I mais corticalizado e menos medular (40 PCF) recebeu um implante de hexágono externo intraoral, sem flange 3,75 mm x 8,5 mm (G1) e um implante de hexágono externo extraoral, com flange 3,75 mm x 8 mm (G2). Em seguida, foram instalados componentes standard com 2 mm de altura de cinta metálica e cilindros metálicos para restauração provisória. Dois extensômetros lineares foram colados na superfície do bloco (mesial e distal de cada implante), e uma carga axial de 100 Ncm em uma máquina de ensaio universal foi aplicada, com cinco medições de microdeformação (µÎµ) para cada implante. Os dados foram submetidos ao teste Shapiro-Wilk para verifi car a homogenidade dos dados e em seguida ao teste t Student. Resultados: as médias e desvios-padrão obtidos foram: G1: 148,2 ± 5,84 e G2: 92,4 ± 11,24 µÆ, com diferença estatística significativa entre os grupos. Conclusão: os implantes extraorais tiveram melhor comportamento mecânico para as cargas axiais do que os implantes intraorais, sendo que a flange melhorou a distribuição da carga na superfície do bloco de poliuretano.

Objectives: to evaluate, by means of extensometry, the influence of the titanium implant flange on the superficial deformation of the bone. Material and methods: a polyurethane block simulating a more corticalized and less spinal type I bone (40 PCF) received an external intraoral hexagon implant with a 3.75 mm x 8.5 mm fl ange (G1) and an extraoral external hexagon implant, with flange 3.75 mm x 8 mm (G2). Subsequently, standard components with 2 mm high of metal strap and metal cylinders were installed for temporary restoration. Two linear strain gauges were glued to the surface of the block (mesial and distal of each implant), and an axial load of 100N in a universal test machine was applied with five microdemorphometric measurements (µÎµ) for each implant. The data were submitted to the Shapiro-Wilks test to verify the homogeneity of the data and then to the t-student test. Results: the means and standard deviations obtained were: G1: 148.2 ± 5.84 and G2: 92.4 ± 11.24 µÎµ, with signifi cant statistical difference between the groups. Conclusion: extraoral implants had better mechanical behavior for axial loads than intraoral implants, and the flange improved the load distribution on the surface of the polyurethane block.

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Objetivo: Uma biomecânica ideal que minimiza a tensão entre implante e osso pode proporcionar sucesso para implantes osseointegrados. Este estudo avaliou a concentração de deformação no tecido circundante e a tensão nos componentes de dois implantes com diferentes conexões protéticas através de métodos in vitro e in silico. Material e Métodos: Vinte blocos de poliuretano foram divididos em dois grupos (n = 10), seguido da instalação de hexágono interno (IH) (AS Tecnologia - Titanium Fix, São José dos Campos, Brasil) ou de implantes cone morse (LT) (Bicon Dental Implants). Para o método da extensometria (SG), foram colocados quatro sensores ao redor dos implantes. Para a análise por elementos finitos (FEA), o mesmo bloco foi modelado e analisado. Foi aplicada uma carga axial (30 kgf) para ambas as metodologias. Os valores de tensão e deformação foram analisados quanto à correlação com o SG. Resultados: Para SG, LT apresentou uma média de deformação mais agressiva (-932) que IH (-632). Para FEA, a LT mostrou menor tensão (-547) que IH (-1169). Conclusão: Para os dois sistemas implantes, os valores de microdeformação capazes de induzir remodelação óssea indesejada não foram medidos. No entanto, para o implante IH, a presença de um parafuso de retenção tem a desvantagem de concentrar a tensão, enquanto um pilar sólido dissipa a carga axial através do implante, o que sugere um melhor desempenho para o grupo LT. (AU)

Objective: An ideal biomechanics minimizes the stress between implant and bone that can provide success for osseointegrated implants. This study evaluated the strain concentration in surrounding tissue and stress in the components of two implants with different prosthetic connections through an in vitro and in silico methods. Methods: Twenty polyurethane blocks were divided into two groups (n=10) followed by the installation of internal hexagon (IH) (AS Technology ­ Titanium Fix, São José dos Campos, Brazil) or locking taper implants (LT) (Bicon Dental Implants). For strain gauge (SG) method, four sensors were placed around the implants. For finite element analysis (FEA), the same block was modeled and analyzed. An axial load (30 kgf) was applied for both methodologies. The values of stress and strain were analyzed for correlation to SG. Results: For SG, LT presented a mean of strain most aggressive (-932) than IH (-632). For FEA, LT showed less stress (-547) then IH (-1169). Conclusion: For two implant's system, microstrain values capable to induce unwanted bone remodeling were not measured. However, for IH implant, the presence of a retention screw has the disadvantage to concentrate stress while a solid abutment dissipates the axial load through the implant that suggests a better performance for LT group(AU)

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BACKGROUND: Information on fracture biomechanics has implications in materials research and clinical practice. The aim of this study was to analyse the influence of non-carious cervical lesion (NCCL) size, restorative status and direction of occlusal loading on the biomechanical behaviour of mandibular premolars, using finite element analysis (FEA), strain gauge tests and fracture resistance tests. METHODS: Ten buccal cusps were loaded on the outer and inner slopes to calculate the strain generated cervically. Data were collected for healthy teeth at baseline and progressively at three lesion depths (0.5 mm, 1.0 mm and 1.5 mm), followed by restoration with resin composite. The magnitude and distribution of von Mises stress and maximum principal stress were simulated at all stages using FEA, and fracture strength was also determined (n = 7 per group). RESULTS: There were significant effects of the lesion size and loading directions on stress, strain and fracture resistance (p < 0.05). Fracture resistance values decreased with increase in lesion size, but returned to baseline with restorations. CONCLUSIONS: Combined assessment of computer-based and experimental techniques provide an holistic approach to characterize the biomechanical behaviour of teeth with both unrestored and restored NCCLs.

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BACKGROUND/AIM: Custom-fitted mouthguards are devices used to decrease the likelihood of dental trauma. The aim of this study was to develop an experimental bovine dentoalveolar model with periodontal ligament to evaluate mouthguard shock absorption, and impact strain and stress behavior. METHODS: A pendulum impact device was developed to perform the impact tests with two different impact materials (steel ball and baseball). Five bovine jaws were selected with standard age and dimensions. Six-mm mouthguards were made for the impact tests. The jaws were fixed in a pendulum device and impacts were performed from 90, 60, and 45° angles, with and without mouthguard. Strain gauges were attached at the palatal surface of the impacted tooth. The strain and shock absorption of the mouthguards was calculated and data were analyzed with 3-way anova and Tukey's test (α = 0.05). Two-dimensional finite element models were created based on the cross-section of the bovine dentoalveolar model used in the experiment. A nonlinear dynamic impact analysis was performed to evaluate the strain and stress distributions. RESULTS: Without mouthguards, the increase in impact angulation significantly increased strains and stresses. Mouthguards reduced strain and stress values. CONCLUSIONS: Impact velocity, impact object (steel ball or baseball), and mouthguard presence affected the impact stresses and strains in a bovine dentoalveolar model. Experimental strain measurements and finite element models predicted similar behavior; therefore, both methodologies are suitable for evaluating the biomechanical performance of mouthguards.

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OBJECTIVES: To evaluate the influence of restorative materials used on the rehabilitation of MOD cavities and loading type, on biomechanical behavior of wedge-shaped (WS) lesions in endodontically treated maxillary premolars. The investigation was conducted by 3D finite element analysis (FEA) and strain gauge test. MATERIALS AND METHODS: Six models were generated, with MOD cavities and endodontic treatment: A (MOD amalgam restoration), R (MOD composite restoration), AL (A + cervical lesion (L)), RL, ALR (A + cervical lesion restored with composite (LR)), and RLR. Each model underwent two compressive loading (100N): axial and oblique-45° angle to the long axis on the buccal cusp. The models were analyzed by von Mises criteria. For strain gauge test, 14 standardized maxillary premolars were treated according to the groups described for FEA. Two strain gauges were bonded on each sample submitted to compressive loading in a mechanical testing machine. RESULTS: A presented higher stress concentration and strain values than R. Oblique loading promoted highest stress concentration and strain rates for all groups. ALR and RLR presented similar stress-strain distribution pattern when compared to A and R. CONCLUSION: The interaction between MOD cavity restored with amalgam and oblique loading propitiated the highest stress concentration and strain values on cervical region and WS lesion. CLINICAL RELEVANCE: The MOD cavity restored with composite resin is a better option than amalgam to improve the biomechanical behavior of wedge-shaped lesion, avoiding dental failure. In addition, the occlusal interferences must be removed, allowing homogeneous contact distribution and preventing WS lesion progression.

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Desde 1980, o comportamento biomecânico dos implantes dentários tem recebido importância em relação às falhas neste sistema de reabilitação devido à sobrecarga oclusal. Através de ferramentas da bioengenharia, vários estudos têm sido realizados para elucidar a influência de diversos fatores sobre a resposta biológica. Ferramentas da bioengenharia, como a análise de elementos finitos (FEA), a extensometria (SGA), a fotoelasticidade (PEA) e a correlação de imagem digital (DIC) são amplamente utilizadas na extrapolação clínica de possíveis soluções mecânicas para implantodontia. Esta trabalho teve como objetivo investigar os métodos de análise de tensão disponíveis para o estudo do comportamento dos implantes dentários através de uma revisão da literatura. Esta revisão começou com uma pesquisa no PubMed dos estudos mais antigos de cada metodologia correlacionadas ao comportamento biomecânico de implantes dentários até 2016. As metodologias FEA, SGA, PEA e DIC são capazes de elucidar o comportamento mecânico deste sistema de reabilitação. No entanto, a combinação de dois ou mais métodos fornece explicações mais detalhadas e evita limitações de uma única metodologia.

Since 1980, the biomechanical behavior of dental implants has received importance regarding the issue of failure in this rehabilitation system due to occlusal overload. Through bioengineering tools, several studies have been conducted to answer about the influence of different factors on the biological response. Bioengineering tools such as finite element analysis (FEA), strain gauge (SGA), photoelasticity (PEA) and digital image correlation (DIC) are widely inspiring clinical extrapolation of possible solutions in the mechanics of implantology. This study has aimed to investigate the available stress analysis methods to study dental implants’ behavior through a literature review. This review started with a PubMed search from the mostly old studies of each methodology correlated to biomechanical behavior of dental implants used with dental implants studies until 2016. FEA, SGA, PEA and DIC methodologies are capable to elucidate the mechanical behavior of this rehabilitation system. However, the combination of two or more methods gives more detailed explanation and avoids limitations of a single methodology.

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O objetivo deste estudo foi avaliar as tensões e deformações in vitro, por meio da fotoelasticidade e da extensometria, em próteses parciais fixas implantossuportadas de três elementos variando o número de pilares: dois e três. O primeiro bloco de poliuretano (modelo mestre 1) recebeu três implantes e o segundo (modelo mestre 2) recebeu dois implantes, todos de hexágono externo. Em seguida, os modelos mestre foram duplicados em resina fotoelástica. Pilares protéticos microunit foram conectados aos implantes com torque de 20 Ncm. Sobre os pilares protéticos dos modelos mestre foram parafusados cilindros plásticos, que receberam estruturas em padrões de resinas, os quais foram fundidos em liga de Ni-Cr (n=10). Quatro extensômetros foram colados na superfície de cada bloco de poliuretano, tangenciando os implantes. Nos modelos mestre e nos modelos fotoelásticos, cada estrutura metálica foi parafusada sobre os pilares protéticos com torque de 10 Ncm. Os dados obtidos na extensometria foram submetidos aos testes estatísticos RM ANOVA e Tukey (5%). As franjas isocromáticas obtidas nos modelos fotoelásticos após cada condição de carga foram registradas com uma câmera digital, visualizadas em um programa de computador e comparadas qualitativamente. Resultados: Houve uma diferença estatística significante entre a quantidade de suporte de uma prótese fixa (p=0,001). Os resultados revelaram que três implantes apresentaram uma melhor distribuição das cargas em qualquer ponto analisado e que a região de pôntico da prótese é o local que apresenta maior diferença na quantidade de deformação (2326,95µÎµ para 2 implantes e 1006,57µÎµ para 3 implantes). Nas imagens fotoelásticas foi possível visualizar uma melhor distribuição das tensões no bloco com 3 implantes. Conclusão: Ambos os métodos apresentaram resultados similares. Esse estudo sugere que uma prótese fixa pode ser suportada por 2 ou 3 implantes(AU)

The present study used photoelastic and strain gauge analysis to compare stress and microstrain to perform an in vitro evaluation of the effect of the numbers of support in a implant-supported fixed partial prostheses with tree elements. The first polyurethane block (master model 1) will contain three implants and the second block (model 2) two of them, all implants have a external hexagon. Then, the master models were duplicated in photoelastic resin. Microunit abutments were connected to the implants and received a 20 Ncm torque. Over the master model plastic prosthetic cylinders were screwed the abutments that received standard patterns cast in Ni-Cr alloy (n=10). Four strain gauges (SG) were bonded in the surface of the block, tangentially to the lateral implants. On the master model and photoelastic model, each metallic structure were screwed onto the abutments with a 10 Ncm torque. The data obtained from the strain gauge were analyzed statistically by RM ANOVA and Tukey's test, with a 5% conventional level of significance. The isochromatic fringes obtained in the photoelastic models after each load condition were recorded with a digital camera, visualized with software to facilitate qualitative analysis. Results: There was statistically significant differences in support of FPD( p=0,001).The results demonstrated that 3 implants has higher stress distribution and in the pontic of FPD we found higher stress (2326,95µÎµ in 2 implants and 1006,57µÎµ in 3 implants).In photoelastic images, 3 implants presented better stress distribution than 2 implants. Conclusions: Both methods found similar results. This study suggests that FPD can be supported by two or three implants(AU)

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OBJECTIVES: Evaluate the effect of environment on post-gel shrinkage (Shr), cuspal strains (CS), microtensile bond strength (µTBS), elastic modulus (E) and shrinkage stress in molars with large class II restorations. METHODS: Sixty human molars received standardized Class II mesio-oclusal-distal cavity preparations. Restorations were made with two composites (CHA, Charisma Diamond, Heraus Kulzer and IPS Empress Direct, Ivoclar-Vivadent) using three environment conditions (22°C/50% humidity, 37°C/50% humidity and 37°C/90% humidity) simulated in custom developed chamber. Shr was measured using the strain gauge technique (n=10). CS was measured using strain gauges. Half of the teeth (n=5) were used to assess the elastic modulus (E) and Knoop hardness (KHN) at different depths using microhardness indentation. The other half (n=5) was used to measure the µTBS. The composites and environment conditions were simulated in a two-dimensional finite element analysis of a tooth restoration. Polymerization shrinkage was modeled using Shr data. The Shr, CS, µTBS, KHN and E data were statistically analyzed using two-way ANOVA and Tukey test (significance level: 0.05). RESULTS: Both composites had similar Shr, CS, µTBS and shrinkage stress. CHA had higher elastic modulus than IPS. Increasing temperature and humidity significantly increased Shr, CS and shrinkage stress. µTBS were similar for groups with lower humidity, irrespective of temperature, and higher with higher humidity. E and KHN were constant through the depth for CHA. E and KHN values were affected by environment only for IPS, mainly deeper in the cavity. Shrinkage stress at dentin/composite interface had high inverse correlation with µTBS. Shrinkage stress in enamel had high correlation with CS. CONCLUSIONS: Increasing temperature and humidity caused higher post-gel shrinkage and cusp deformation with higher shrinkage stresses in the tooth structure and tooth/restoration interface for both composites tested. The chamber developed for simulating the oral environment conditions will improve the realism of in vitro studies. Clinical significance Simulating oral temperature and humidity is important to better determine the biomechanical behavior of composite resin restoration. Avoiding high humidity during restorative procedures using rubber dam isolation may reduce cuspal deformation and shrinkage stress and improve the bonding strength of posterior composite restorations.

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Objetivo: analisar a influência da distribuição dos implantes nas microdeformações da mandíbula, no carregamento da infraestrutura da prótese total parafusada. Material e métodos: foram utilizados seis modelos de mandíbulas confeccionados em poliuretano, distribuídos em três grupos com dois modelos cada, nos quais foram instalados cinco implantes (protocolo de Brånemark) utilizando três configurações distintas. Grupo I: os implantes foram instalados com espaçamentos equidistantes de 9 mm entre eles. Grupo II: implantes intermediários foram instalados a 8 mm do implante mais distal. Grupo III: implantes intermediários foram instalados a 8 mm do implante mais anterior. Extensômetros (strain gauges) foram fixados nas áreas adjacentes aos implantes, para determinar as microdeformações ocorridas após o carregamento, e seis barras de Ni-Cr, que foram parafusadas nos implantes, foram confeccionadas. Uma força de 200 N foi aplicada em três pontos da barra: parte anterior, cantiléver direito e cantiléver esquerdo. As microdeformações apresentadas sob a forma de gráficos foram tabuladas e levadas a teste estatístico. Resultados: as maiores microdeformações ocorreram quando foram carregadas as extremidades (direita ou esquerda) da barra, e que não houve diferença significativa de microdeformações entre as três configurações estudadas. Conclusão: a distribuição de carga numa prótese total fixa parafusada sobre implantes ainda é complexa e deveria ser estudada em modelos clínicos correspondentes.

Objective: to analyze the influence of implant distribution on mandibular microdeformation upon loading of an infrastructure fabricated for a complete fixed, screw-retained, implant-supported dental prosthesis. Material and methods: six polyurethane mandibular models were made and distributed into three groups (n=2). Each model received five dental implants. Three distinct configurations were used; Group I: all implants were positioned 9 mm apart each other; Group II: the most central implants were placed 8 mm from the most distal implant. Group III: the most central implants were placed 8 mm from the most anterior implant. Strain gauges were affixed at implant adjacent areas to determine the microstrain values after loading. Six cast and laser-welded Ni-Cr infrastructures were fabricated and fastened to the dental implants with a 10 Ncm torque. A 200 N load was applied at three predetermined points: anterior portion, and at the right and left cantilevers. The Kruskal-Wallis test was used to compare microstrain values among groups. Results: 1) Forces applied at the cantilever induced microstrain around all dental implants, 2) The greatest deformations were observed at the right and left extremities and 3) With forces in the anterior portion, great deformation values were observed at the bone adjacent to the most posterior implants. However, no differences were seen for microstrain values among groups. Conclusions: load distribution for complete fixed, screw-retained, implantsupported prosthesis is still a complex factor and must be investigated in correspondent clinical models.

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A reabilitação protética de pacientes desdentados é uma área da Odontologia amplamente estudada por pesquisadores do mundo todo, e com o desenvolvimento dos implantes osseointegrados surgiram muitas perguntas sobre o desempenho das próteses instaladas sobre estes. Conhecer o comportamento mecânico do conjunto coroa unitária, intermediário, implante e tecido de suporte é importante para entender o processo de transmissão de forças e suas consequências, processos estes que ainda não estão totalmente compreendidos. O objetivo deste trabalho foi verificar a deformação gerada no intermediário e no osso peri-implantar após aplicação de uma carga inclinada sobre coroas unitárias metalocerâmicas. Foi utilizado um modelo mestre de poliuretano, simulando o osso mandibular, com um implante hexágono externo de 3,75mm x13 mm de comprimento, no qual foi fixado um intermediário multi-unit. O trabalho foi realizado com 3 grupos de 4 coroas cada, divididos de acordo com o tipo de cilindro e liga de fundição (cilindros de ouro sobrefundidos com liga de PdAg, cilindro de acrílico fundido com liga de NiCoCr e cilindros de CoCr usinado sobrefundidos com liga de NiCoCr). Cada corpo de prova foi submetido cinco vezes à aplicação de carga oblíqua de 15 e 30 graus no centro da oclusal de cada coroa com uma força de 300N em uma máquina universal de ensaios. Foram realizadas leituras das deformações geradas no intermediário e no poliuretano, com o uso de extensômetros lineares elétricos (strain gauges) os quais foram colados em três faces do intermediário (Disto lingual, Mesio lingual, Vestibular) e nas superfícies mesial, vestibular, distal e lingual do osso simulado ao redor do implante. Os dados obtidos foram submetidos à análise de variância a 3 critérios (ANOVA) e o teste de Tukey, utilizando um nível de significância (p<0,05). Os resultados mostraram que entre as duas angulações utilizadas existiram diferenças estatísticas significantes. Os valores médios de deformação se...

The prosthetic rehabilitation of edentulous patients is a dental area widely studied by worldwide researchers, and through the development of dental implants, appear many questions about the performance of prostheses installed on them. Knowledge of the mechanical behavior of the integration between single crown, abutment, implant and support tissue is very important to understand the forces transmission process and its consequences but these processes are not fully understood. The objective of the present study was to evaluate the deformation generated in the abutment and simulated peri-implant bone after application of an oblique load on metal-ceramic crowns. A polyurethane master model was used to simulate the jawbone with an implant external hexagon 3.75 mm x13 mm length, which was fixed in a multi-unit abutment. The study was conducted with twelve metal ceramic crowns divided according to type of cylinder and casting alloy, Group 1: Gold cylinder cast with PdAg alloy; Group 2: Acrylic cylinder cast with NiCoCr alloy; Group 3: CoCr cylinder cast with NiCoCr alloy, thus forming three groups of four sample each. Each specimen was subjected five times the application of oblique load of 15 and 30 degrees in the center of the occlusal of each crown with a 300N force in a universal testing machine. Readings were taken of the deformations generated in the abutment and bone simulated by polyurethane, with the use of electric linear strain gauges which have been positioned on three sides equidistant to each other to measure microstrains at abutment (disto-lingual, meso-lingual, Vestibular) and the simulated bone around each implant received four strain gauges, positioned on the mesial, distal, buccal and lingual aspects. The data were submitted to analysis of variance to 3 criteria (ANOVA) and Tukey test, using a significance level (p <0.05). The results showed that between the two angles tested there were significant statistical differences...

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O objetivo deste estudo foi avaliar a transmissão da carga mastigatória ao osso de suporte em próteses implantossuportadas em função do cantiléver, variando o tipo de pilar (Micro-Unite Ucla). A partir de dois modelos de poliuretano (norma ASTM F –1839), foram inseridos três implantes em cada, a uma distância de 8 mm, que conformaram os grupos: 1) implantes de hexágono externo e pilares Micro-Unit; 2) implantes de hexágono externo e pilares Ucla. Foram confeccionadas estruturas protéticas em resina acrílica ativada quimicamente sob cilindros com base de Co-Cr, que foram fundidas pela técnica convencional à brasagem. Foram fixados extensômetros no poliuretano entre os implantes e um na distal do implante mais próximo ao cantiléver. Em uma máquina de ensaio universal (2000RK – Kratos, São Paulo, Brasil), foi realizada a aplicação da carga de 150 N. A carga foi aplicada entre os implantes e no cantiléver nos intervalos de 5, 10, 15, 20 e 25 mm. Os dados obtidos foram analisados estatisticamente para cada extensômetro e levando em consideração a extensão do cantiléver. Quanto maior a extensão do cantiléver, maior a deformação superficial do osso ao redor do implante mais distal. A utilização do componente tipo Micro-Unit apresentou valores de deformação inferiores em relação ao Ucla.

Objectives: to evaluate transmission of masticatory loads according to different prosthetic implant abutment and cantilever lengths. Material and methods: two polyurethane models (ASTM F-1839) received 3 external hex dental implants 8 mm each apart divided into two groups: 1) Micro-Unit and, 2) Ucla. Metallic frameworks were prepared using acrylic resin and cast over CoCr prosthetic cylinders. Strain gauges were attached at the polyurethane-abutment interface and at the distal part of the implant near the cantilever. After, a 150 N load (2000 RK, Kratos, São Paulo, Brazil) was applied at 15, 20, and 25 mm from the most distal implant. Statistical analysis considered abutment type and cantilever lengths. Results: longer cantilevers generate more deformation in the distal implant. Deformation values at Micro-Unit were lower than at Ucla abutment type.

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Este estudo in vitro analisou, por meio da extensometria, as micro deformações que ocorreram ao redor de implantes de hexágono externo ao variar o tipo de coifa, plástica e usinada, após o aperto dos parafusos de retenção da prótese. No bloco de poliuretano três implantes de hexágono externo foram inseridos linearmente. Pilares protéticos Microunit foram conectados aos implantes com torque de 20 Ncm. Coifas plásticas (n=5) e usinadas (n=5) receberam enceramentos padronizados e foram fundidos em monobloco em liga de cobalto-cromo. No bloco de poliuretano, tangenciando os implantes foram colados os extensômetros, sendo dois para o central. As estruturas metálicas foram fixadas aos pilares protéticos com parafusos de retenção com torque de 10 Ncm, quando foram registradas as micro deformações (με) em cada extensômetro. Os valores médios obtidos dos extensômetros para as coifas plásticas foram de 363,37 με ± 237,66 e para as usinadas de 338,12 με ± 223,01. Estes foram avaliados pelo teste t-Student, que demonstrou não haver diferença estatística significante ao variar o tipo de coifa (p=0,867). Concluiu-se que, para implantes de hexágono externo posicionados linearmente, o tipo de coifa não influenciou na quantidade de micro deformação gerada após o aperto dos parafusos de retenção da prótese.

The objective of this in vitro study was quantify the micro strain development around the external hexagon implants, varying the type of prosthetic coping. Three implants of external hexagon were inserted into one polyurethane block. Microunit abutments were screwed onto the implants, applying a torque of 20Ncm. Plastic prosthetic copings (n=5) and machined copings (n=5) which received standard wax patterns were cast in Co-Cr alloy. On the surface of poliurtehane block tangentially the implants were bonded the strain gauges, two to the center implant. The super structure’s occlusal screws were tightened onto microunit abutments with 10 Ncm torque, the magnitude of micro strain was recorded. The mean values of each strain gauge of each plastic copings were 363,37 με ± 237,66 and the machined copings were 338,12 με ± 223,01. The data were analyzed statistically by t-Student test. No statistically significant difference was found between the prosthetic copings (p=0,867) It was concluded that to external hexagon implants in line placement, the type of coping presented similar magnitude of micro strain after prosthetic occlusal screw was tightened

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RESUMO

O implante dental depende do osso de suporte para sua estabilidade e ongevidade funcional. O comportamento mecânico e a estrutura trabecular do osso afetam a interface com o implante. Tal conhecimento pode fornecer uma base para melhoramentos na função e desenho dos implantes atuais minimizando a reabsorção da crista óssea e falha na junção osso-implante. Desta forma a correta quantificação das forças que atuam sobre o sistema de implante e principalmente no osso de suporte ao qual ele está inserido é importante para o entendimento da biomecânica possibilitando que intervenções possam ser realizadas pelos profissionais visando assim à longevidade das próteses implanto-suportadas bem como dos implantes que as sustentam. Por essa razão, a proposta deste trabalho foi avaliar, com auxílio de extensômetros elétricos, se o processo laboratorial de confecção de coroas metalocerâmicas resulta em alterações das tensões no osso ao redor dos implantes. Para isto foi utilizado um modelo de poliuretano em forma de U simulando o osso mandibular com dois implantes de hexágono externo de 3,75mm de diâmetro por 13 mm de comprimento, nos quais foram fixados intermediários multi-unit. Os corpos de prova foram confeccionados com dois tipos de ligas odontológicas - Cobalto-Cromo e Paládio-Prata - e três tipos de cilindros protéticos calcinável, usinado de Cobalto-Cromo e usinado de Ouro. As leituras de deformação foram realizadas em dois momentos: 1- após a fundição das infra-estruturas e 2 após estas infra-estruturas terem recebido cobertura cerâmica. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. Os resultados mostraram que, após a aplicação da cobertura cerâmica, ocorreu piora da condição de assentamento aos intermediários. O mesmo não foi detectado quando se avaliou a deformação do osso simulado, já que os valores de deformação não indicaram...

The dental implant depends on the supporting bone for its stability and functional longevity. Mechanical behavior and trabecular bone structure affect the interface with the implant. Such knowledge may provide a basis for improvements in the current implant function and design, decreasing bone crest resorption and failure at bone-implant junction. Adequate quantification of forces that act upon the implant system and mainly on the supporting bone is important for understanding the biomechanics, allowing the intervention by professionals with the purpose of achieving the longevity of implant-supported prostheses. Therefore, this work aims at evaluating, with the aid of strain gauges, whether the laboratorial process of metal ceramic crown fabrication results in changes of the tensions around the implants. A U-shaped polyurethane model simulating the mandibular bone with two 3.75-mm diameter and 13-mm length external hexagon implants were used with fixed multi-unit abutments. Specimens were prepared with two types of dental alloys - cobalt-chromium and silver-palladium - and three types of prosthetic cylinder castable plastic, prefabricated in cobalt-chromium or gold. The deformation readings were performed in two moments: 1- after framework casting and 2- after ceramic layering of the framework. The tests were performed with the framework screwed onto the abutments at 10Ncm using an electronic torque device. The results showed that the ceramic layering worsened the fit between the crowns and the abutments. The same was not detected when bone deformation was evaluated since the values were not statistically different.

Assuntos

RESUMO

O implante dental depende do osso de suporte para sua estabilidade e ongevidade funcional. O comportamento mecânico e a estrutura trabecular do osso afetam a interface com o implante. Tal conhecimento pode fornecer uma base para melhoramentos na função e desenho dos implantes atuais minimizando a reabsorção da crista óssea e falha na junção osso-implante. Desta forma a correta quantificação das forças que atuam sobre o sistema de implante e principalmente no osso de suporte ao qual ele está inserido é importante para o entendimento da biomecânica possibilitando que intervenções possam ser realizadas pelos profissionais visando assim à longevidade das próteses implanto-suportadas bem como dos implantes que as sustentam. Por essa razão, a proposta deste trabalho foi avaliar, com auxílio de extensômetros elétricos, se o processo laboratorial de confecção de coroas metalocerâmicas resulta em alterações das tensões no osso ao redor dos implantes. Para isto foi utilizado um modelo de poliuretano em forma de U simulando o osso mandibular com dois implantes de hexágono externo de 3,75mm de diâmetro por 13 mm de comprimento, nos quais foram fixados intermediários multi-unit. Os corpos de prova foram confeccionados com dois tipos de ligas odontológicas - Cobalto-Cromo e Paládio-Prata - e três tipos de cilindros protéticos calcinável, usinado de Cobalto-Cromo e usinado de Ouro. As leituras de deformação foram realizadas em dois momentos: 1- após a fundição das infra-estruturas e 2 após estas infra-estruturas terem recebido cobertura cerâmica. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. Os resultados mostraram que, após a aplicação da cobertura cerâmica, ocorreu piora da condição de assentamento aos intermediários. O mesmo não foi detectado quando se avaliou a deformação do osso simulado, já que os valores de deformação não ndicaram...

The dental implant depends on the supporting bone for its stability and functional longevity. Mechanical behavior and trabecular bone structure affect the interface with the implant. Such knowledge may provide a basis for improvements in the current implant function and design, decreasing bone crest resorption and failure at bone-implant junction. Adequate quantification of forces that act upon the implant system and mainly on the supporting bone is important for understanding the biomechanics, allowing the intervention by professionals with the purpose of achieving the longevity of implant-supported prostheses. Therefore, this work aims at evaluating, with the aid of strain gauges, whether the laboratorial process of metal ceramic crown fabrication results in changes of the tensions around the implants. A U-shaped polyurethane model simulating the mandibular bone with two 3.75-mm diameter and 13-mm length external hexagon implants were used with fixed multi-unit abutments. Specimens were prepared with two types of dental alloys - cobalt-chromium and silver-palladium - and three types of prosthetic cylinder castable plastic, prefabricated in cobalt-chromium or gold. The deformation readings were performed in two moments: 1- after framework casting and 2- after ceramic layering of the framework. The tests were performed with the framework screwed onto the abutments at 10Ncm using an electronic torque device. The results showed that the ceramic layering worsened the fit between the crowns and the abutments. The same was not detected when bone deformation was evaluated since the values were not statistically different.

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